JPH0547841Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention uses a spool that slides inside a valve when supplying hydraulic oil to the oil chamber of an actuator such as a cylinder, or when discharging hydraulic oil from the oil chamber. The present invention relates to a direct-acting servo valve that controls the supply and discharge of hydraulic oil by

[Conventional technology]

In general, a direct-acting servo valve connects a coil bobbin having a coil to one end of a spool, and applies current to the coil to displace the spool and switch between a supply port and a discharge port communicating with the actuator.

For example, in the servo valve shown in FIG. 2 developed by the present applicant, a coil bobbin 3 having a coil 2 is connected to one end of a spool 1, and the spool 1 is movably inserted into a valve housing 4.
The spool 1 is balanced by interposing springs 5 and 6 that bias in opposite directions on both sides of the coil 2, and when a current is applied to the coil 2, the spool 1 is moved left and right depending on the magnitude and direction of the current. port 7,
8, 9, and 10.

Similarly, in the direct-acting type servo valve shown in FIG. 3 disclosed in Japanese Utility Model Application Publication No. 60-167209, a coil bobbin 14 having a coil 17 is coupled to one end of a spool 22, and a coil bobbin 14 having a coil 17 is connected to one end of the spool 22. The spool 22 is movably inserted into the valve housing 20 and the magnet 51, and a spool displacement detector 56 is provided at the end of the spool 22 on the magnet side. , by applying current to the coil 17, the spool is moved left and right to connect the ports 23a and 23b.
This is to switch between.

In the above conventional technology, the spools 1 and 2
Depending on the orientation of the ends of the springs 5, 6, 10, 10 in contact with the springs 2, a radial force acts on the spools 1, 22, thereby generating a rotational moment on the spools 1, 22, causing the spools to rotate. oscillate.
For this reason, as a conventional method to prevent spool oscillation,
In the conventional example shown in FIG. 2, magnetic fluid is applied between the coil 2 and the magnet 12 for damping, and similarly, in the conventional example shown in FIG. gives a damping force to

[The problem that the idea attempts to solve]

In the conventional example shown in Fig. 2 above, since the springs 5 and 6 are arranged at both ends of the spool 1, the distance from the center of rotation to the point of force application becomes long, the rotational moment becomes large, and the magnetic There is a problem in that sufficient damping cannot be achieved only by applying fluid.

In the conventional example shown in FIG. 3, the springs 16 and 17 are located close to each other, so there is no problem like that shown in FIG. There is a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a direct-acting servo valve that can reduce the rotational moment caused by the spring, has a simple structure, and reduces costs.

[Means to solve the problem]

In order to achieve the above purpose, the configuration of the present invention is as follows:
In a direct-acting servo valve, a coil bobbin with a coil electromagnetically coupled to a field magnet is connected to a spool, and the spool is displaced by the electromagnetic attraction effect caused by applying current to the coil to switch ports. The spool is biased in opposite directions by intervening two opposing springs close to each other, and the end of the spool opposite to the coil bobbin is inserted into the magnet, and the outer periphery of the spool end is connected to the magnet. The feature is that a magnetic fluid is interposed in the gap between the two.

[Effect]

When the coil is energized, the interaction between the magnetic force from the magnetic circuit of the force motor and the current flowing through the coil causes the coil bobbin to receive an axial force depending on the direction of the current, which causes the spool connected to the coil bobbin to release the spring. is displaced in the axial direction to a position that balances the spring force. The magnitude of this displacement is proportional to the magnitude of the current flowing through the coil. This gives the valve opening degree and controls the hydraulic pressure.

When the spool is displaced by the thrust of the coil bobbin, a force in the direction opposite to the direction of displacement of the spool acts due to the magnetic fluid applied between the magnet and the spool. Since the springs are arranged close to each other, the distance between them is short, reducing the moment relative to the spool and reducing the cause of oscillation.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

The direct-acting servo valve includes a force motor 24, a valve housing 20, and a partition wall 25.

The force motor 24 includes a housing 26,
27, a pole 28, a field magnet 29, a yoke 30, and a coil bobbin 31.
A hole 34 is formed in the center of 8 in the lateral direction.

A coil 32 is wound around the coil bobbin 31, and when a current is passed through the coil 32, the coil bobbin 31
is adapted to move in the axial direction, and the direction of movement can be selected by switching the direction of current flowing through the coil 32 to the plus side or the minus side. The force that drives this coil bobbin 31 is the magnetic flux density of the magnet 29,
It is proportional to the effective length of the coil 32 and the magnitude of the current. A screw hole 33 is screwed into the center of the housing 26 and the pole 28, and the screw 33 is in contact with a push rod 35 movably inserted into the hole 34.

The valve housing 20 is connected to the force motor 24 . The valve part 36 consists of a valve housing 20, a sleeve 37, and a spool 38, and the valve housing 20 has an oil passage 39,
40 is formed, and a sleeve hole 41 is bored in the axial direction, the sleeve 37 is fitted into this sleeve hole 41, and another sleeve 37a is provided inside this sleeve 37. The spool 38 is slidably inserted within this sleeve 37a. A valve hole 42 is bored in the axial direction in the sleeve 37a, and the spool 38 is inserted into this valve hole 42, and a pressure supply port P and tank ports Ta and Tb are opened to this valve hole 42. have. Further, holes Q and R are bored in the radial direction in the sleeves 37 and 37a, and the inner ends of the holes Q and R open to the valve hole 42, and the other end opens to the oil passage formed in the valve housing 20. 39 and 40, respectively. Also, spool 3
8 has a small diameter portion and a land, and is connected to the coil bobbin 31 via a connecting rod 43 at one end.

The connecting rod 43 passes through the center of the coil bobbin 31, for example, and integrally connects the two.

A magnet 47 is arranged on the right side of the valve housing 20 and coupled to the sleeve 37a, and the right end of the spool 38 is movably inserted into the center hole of the magnet 47, so that the outer periphery of the end of the spool 38 and the hole of the magnet 47 are inserted into the center hole of the magnet 47. A magnetic fluid 48 is applied in the gap with the inner circumference.

A spring 44 is inserted into the hole 34 and is interposed between the push rod 35 and the coil bobbin 31. A seat 45 is provided at the left end of the spool 38, and another spring 46 is interposed between the seat 45 and the sleeve 37a, this spring 46 approaches the spring 44, and both move toward the spool 38 in opposite directions. is energized.

One spring 46 is a spring seat 46
The other spring 44 urges the spool 38 to the right through the coil bobbin 31.
The spool 38 is held in the neutral position with a force of 4.46.

The tension of the springs 44, 46 is arbitrarily adjusted by the screw 33 and push rod 35, and the neutral position of the spool 38 is also set.

When the spool 38 moves towards the force motor 24, the holes Q and R open to the valve hole 42, the pressure port P communicates with the oil passage 39 via the valve hole 42 and hole Q, and the tank port Tb communicates with the oil passage 40 via the valve hole 42 and hole R. Conversely, when the spool 38 moves to the right, the pressure supply port P communicates with the oil passage 40 via the valve hole 42, and the tank port Ta communicates with the oil passage 39 via the valve hole 42.

When the coil 32 is energized, the force motor 24
Due to the interaction between the magnetic force generated by the magnetic circuit and the current flowing through the coil 32, the coil bobbin 31 receives an axial force depending on the direction of the current, and this causes the spool 38 coupled to the coil bobbin 31 to move between the springs 44 and 46. It is displaced in the axial direction to a position where it balances with the other. The magnitude of this displacement is proportional to the magnitude of the current flowing through the coil, which gives the valve opening and controls the hydraulic pressure. Therefore, when the spool 38 is displaced to the left or right by the thrust of the coil bobbin 31, the magnetic fluid interposed between the magnet 47 and the end of the spool 38 generates a force in the opposite direction to the displacement direction of the spool 38. This damps the spool 38 and prevents it from oscillating.

Moreover, the springs 44 and 46 are connected to the spool 38.
Since they are close to one end facing each other, the distance between them is short, and the moment against the spool 38 caused by poor processing of the spring or unbalance of the spring force is small, which is the cause of oscillation against the spool 38. is being reduced.

[Effect of idea]

According to the present invention, the following effects can be obtained.

One end of the spool is movably inserted into the magnet, and the magnetic fluid is interposed in the gap between the spool and the magnet, so when the spool is displaced, the magnetic fluid applies a force to the spool in the opposite direction to the displacement direction. , the vibrations of the spool are damped and oscillations are prevented.

Moreover, the structure of the magnet and magnetic fluid provided at the end of the spool is simple, and costs can be reduced.

At the other end of the spool, two opposing springs are placed close to each other, so the distance between the two springs is short, and the moment acting on the spool by each spring is reduced, causing oscillation on the spool. factors are reduced.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of a direct acting servo valve according to an embodiment of the present invention, and FIGS. 2 and 3 are longitudinal sectional front views of a conventional direct acting servo valve. 31...Coil bobbin, 32...Coil, 38
...Spool, 44, 46 ...Spring, 47
...Magnet, 48...Magnetic fluid.

Claims (1)

[Scope of utility model registration request] In a direct-acting servo valve, a coil bobbin with a coil electromagnetically coupled to a field magnet is connected to a spool, and the spool is displaced by the electromagnetic attraction effect caused by applying current to the coil to switch ports. The spool is biased in opposite directions by intervening two opposing springs close to each other, and the end of the spool opposite to the coil bobbin is inserted into the magnet, and the outer periphery of the spool end is connected to the magnet. A direct-acting servo valve characterized by having a magnetic fluid interposed in the gap between the valves.